High rate electrochemical devices

ABSTRACT

A device and system useful for highly efficient chemical and electrochemical reactions is described. The device comprises a preferably porous electrode and a plurality of suspended nanoparticles diffused within the void volume of the electrode when used within an electrolyte. The device is suitable within a system having a first and second chamber preferably positioned vertically or in other special arrangements with respect to each other, and each chamber containing an electrode and electrolyte with suspended nanoparticles therein. When reactive metal particles are diffused into the electrode structure and suspended in electrolyte by gasses, a fluidized bed is established. The reaction efficiency is increased and products can be produced at a higher rate. When an electrolysis device can be operated such that incoming reactants and outgoing products enter and exit from opposite faces of an electrode, reaction rate and efficiency are improved. Ideally, this device and system can be used to rapidly produce significant quantities of high purity hydrogen gas with minimal electricity cost.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.11/716,375, filed on Mar. 9, 2007.

BACKGROUND OF THE INVENTION

1. Technical Field

The inventions disclosed herein generally relate to improvedelectrochemical systems and their use and, in particular, to waterelectrolysis devices for the production of high purity hydrogen andoxygen, and catalysts for these devices which promote increasedelectrical and cost efficiency, and methods of using such devices andfor the production of hydrogen and oxygen.

2. Related Art

Hydrogen is a renewable fuel that produces zero emissions when used in afuel cell. In 2005, the Department of Energy (DoE) developed a newhydrogen cost goal and methodology, namely to achieve$2.00-3.00/gasoline U.S. gallon equivalent (gge, delivered, untaxed, by2015), independent of the pathway used to produce and deliver hydrogen.The principal method to produce hydrogen is by stream reformation.Nearly 95% of the hydrogen currently being produced is made by steamreformation, where natural gas is reacted on metallic catalyst at hightemperature and pressure. While this process has the lowest cost, fourpounds of the greenhouse gasses carbon monoxide (CO) and carbon dioxide(CO₂) are produced for every one pound of hydrogen. Without furthercostly purification to remove CO and CO₂, the hydrogen fuel cell cannotoperate efficiently.

Alternatively, 5% of hydrogen production is from water electrolysis.This reaction is the direct splitting of water molecules to producehydrogen and oxygen. Note that greenhouse gasses are not produced inthese reactions. In this process, electrodes composed of catalystparticles are submersed in water and energy is applied to them. Usingthis energy, the electrodes split water molecules into hydrogen andoxygen. Hydrogen is produced at the cathode electrode which acceptselectrons and oxygen is produced at the anode electrode which liberateselectrons. The amount of hydrogen and oxygen produced by an electrode isdictated by the current supplied to the electrodes. The efficiencydepends upon the voltage between the two electrodes, and is proportionalto the reciprocal of that voltage. That is to say; efficiency increasesas the voltage decreases. A more catalytic system will have a lowervoltage for any one current, and therefore be more efficient inproducing hydrogen and oxygen. If the catalyst is highly efficient,there will be minimal energy input to achieve a maximum hydrogen output.Unfortunately, this process is currently too expensive to compete withsteam reformation due low efficiency and the use of expensive catalystsin the electrodes.

Devices that are configured to electrochemically convert reactants intoproducts when energy is applied are generally known as electrolyzers.For an electrolyzer to operate with high efficiency, the amount ofproduct produced during reaction should be maximized relative to theamount of energy input. In many conventional devices, low catalystutilization in the electrodes, cell resistance, inefficient movement ofelectrolyte, and inefficient collection of reaction products from theelectrolyte stream contribute to significant efficiency loss. In manycases, low efficiency is compensated for by operating the cell at a lowrate (current). This strategy does increase efficiency, however, it alsolowers the amount of products that can be produced at a given time. Theelectrolyzer described in the preferred embodiments can operate both athigh rates and efficiencies.

Fluidized bed reactors (FBRs) have been designed to carry out chemicalreactions that take place between materials of the same or differentphases (solids, liquids and/or gasses). In an FBR that contains catalystparticles, a gas or liquid is passed upwardly through the FBR withenough flow rate to cause suspension of the catalyst particles. WhileFBRs have been used in the chemical industry because of their positiveheat and mass transfer characteristics, use of FBRs remain unexplored inconjunction with electrochemical cells.

SUMMARY OF THE INVENTION

In one aspect of the invention, there is provided a device suitable foruse in an electrochemical and/or catalytic application, the devicecomprising a metal component, preferably having substantial void volume,a reaction medium to which the metal component is at least partiallyexposed during use, and a plurality of reactive metal nanoparticlessuspended in the reaction medium when the device is in use and diffusedinto the metal component when the metal component preferably has saidsubstantial void volume and when the device is in use. The reactionmedium is preferably an electrolyte, with metal components comprising ananode and a cathode to form an electrochemical cell.

The invention thereby provides a high-surface area electrode. In oneembodiment, the electrode comprises a porous or reticulate metal platecombined with catalytic metal particles, preferably at the nanoscale.The plate preferably includes some void volume to allow infusion of aplurality of metal nanoparticles. More preferably, the plates areporous, such as sintered or reticulate, and most preferably theycomprise metal foams.

When immersed within an electrolyte, the metal particles can floatfreely and can substantially infuse into the porous/reticulate metalplate to create an electrode with extremely high surface area.

The electrodes in this invention can be applied to a variety of devices,including a hydrogen generation electrode in a water electrolyzersystem. In such an embodiment, the electrode can function as a fluidizedbed. At least one advantage is that the electrode can be operated atcurrents (rates) exceeding 1 A/cm² and efficiencies in excess of 65%(measured by voltammetric or galvanometric electrochemical testing.),which in turn means that large amounts of hydrogen can be produced usingless electricity. Typical electrodes have a far lower surface area andthus cannot operate at rates significant enough to produce largequantities of hydrogen. Other advantages may include, depending upon theconfiguration, circumstances, and environment, the ability to scale theelectrode to a wide variety of sizes, a high rate of hydrogenproduction, and the ability to minimize agglomeration by usingnano-sized particles. The fluidized bed reactor of the inventionpreferably produces from about 0.1 to about 3, more preferably fromabout 1 to about 3 gge/hr/m² of hydrogen. A gge is a “U.S. gallon ofgasoline equivalent”

One embodiment of the invention provides an electrochemical system,comprising: a first chamber and a second chamber, the first chamberbeing separated or partitioned from the second chamber by a separator,such as a membrane, the first chamber comprising an electrode,electrolyte, and metal catalyst particles arranged such that, when inoperation, a fluidized bed may be established and gaseous products maybe removed from the first chamber, such as from an upper portionthereof, the second outer chamber comprising an electrode, electrolyte,and metal catalyst particles arranged such that, when in operation, afluidized bed may be established, and gaseous products may be removedfrom the second chamber, such as from an upper portion thereof.

The chambers can be arranged in a variety of ways, such as one at leastpartially above the other; one at least partially surrounding the other;one laterally displaced with respect to the other and one coiled atleast partially around the other.

The reaction efficiency may be enhanced depending on the metalnanoparticles chosen. Efficiencies of at least 75%, preferably at least85% may be achieved. Preferably, the plurality of reactive metalparticles have an oxide shell. The reactive particles preferablycomprise a metal selected from the group consisting of metals fromgroups 3-16, lanthanides, combinations thereof, and alloys thereof, andmost preferably the metal nanoparticles are nickel, iron, combinationsthereof, and alloys thereof.

The anode and cathode chambers may be filled with electrolyte thatpreferably contains a plurality of reactive and conductive metalnanoparticles. Preferably, the metal nanoparticles are on average lessthan 100 nm in diameter Average particle size is typically measured byTEM microscopy and GAA analysis, and is more preferably less than 50 nmin diameter, such as from 10-30 nm. The reaction efficiency may beenhanced depending on the metal nanoparticles chosen. Nickel or iron ispreferred.)

Preferably, the generated anode and cathode gasses flow through thecontainer in a manner that suspends the nanoparticles within the fluid,creating a fluidized bed. Most preferably, the bed is fluidized by thereaction products. At least some advantages of this configurationinclude, (i) elimination of pumps via direct extraction of gasses fromthe container, such as via upper vents, and the self propagating natureof the fluidized bed, (ii) ease of keeping hydrogen and oxygen gassesseparated, (iii) ease of controlling temperature and pressure, (iv)simple design, and (v) less expensive per unit of hydrogen produced, toname a few.

The invention also provides a method of operating an electrochemicalcell, which cell comprises an anode chamber containing electrolyte andan anode, a cathode chamber containing electrolyte and a cathode, whichmethod comprises suspending reactive metal particles, preferablynanoparticles, in the anode chamber and/or the cathode chamberelectrolyte, applying electric current to the anode and the cathode.Preferably, the suspension of reactive nanoparticles is provided in atleast the cathode chamber, more preferably in both chambers, and thechambers are configured so that, in use, the suspension(s) act in thenature of a fluidized bed to transport gases from the chamber(s). Thus,the invention provides a method of generating hydrogen from water byelectrolysis, comprising suspending reactive metal nanoparticles in achamber containing a cathode and electrolyte, applying electric currentto the cathode and to an anode in a chamber containing the anode andelectrolyte, producing hydrogen in the cathode chamber and forming inthat chamber from the hydrogen, electrolyte and particles a system akinto a fluidized bed whereby the hydrogen bubbles upwardly through theelectrolyte, the method further comprising collecting the hydrogen soproduced. These methods are applicable to the devices, systems,compositions and components described herein in connection with otherembodiments of the invention.

In another aspect of the invention, a new electrochemical device isprovided, preferably a water electrolysis device. Unlike traditionalelectrolyzers, such as that shown in FIG. 1, one embodiment of theinventive electrochemical device system may be oriented horizontallyrather than vertically. With such an arrangement, electrolyte may bemoved through a lower chamber, with oxygen being generated on a lowerelectrode. A deflector is preferably placed in the electrolyte stream toensure removal of all generated oxygen from the system. Oxygen may bescrubbed from the electrolyte before it is circulated back into thesystem. In at least one embodiment, water generated from the reactioncan move through a separator membrane to the upper chamber. An upperchamber electrode produces hydrogen gas. Because hydrogen gas is lessdense than the electrolyte, the hydrogen may bubble upwards and can thenbe removed from the system. Preferably, a fluidized bed is establishedin the upper chamber employing catalytic nanoparticles.Contemporaneously, hydroxyl ions (OH—) are generated and may movedownwardly through the separator for consumption at the lower chamberelectrode. At least some advantages include, depending upon theconfiguration, circumstances, and environment, (i) that only half of thesystem may need pumping (unless the device is oriented on an angle, inwhich case no pumping may be necessary) whereas traditional systems needtotal pumping; (ii) half the pumping means half the parasitic losses;(iii) there is no need for a gas separator in the upper chamber; gasfreely moves upward because it is less dense, and (iv) ions move fromthe bottom of the electrode while hydrogen escapes from the top, whichgives a lower ionic resistance.

In yet another aspect of the invention, a fluidized bed electrolyzer maybe provided that comprises a corrosion resistant container that houses acylindrical separator. In one embodiment, porous anode and cathodeelectrodes may be disposed on the outer and/or inner circumference ofthe separator.

In the preferred embodiments, the individual anode or cathode electrodesin the cell may be fluidized, or both may be fluidized. Preferably, bothelectrodes are fluidized. A number of electrolyzer cells may beinterconnected to function as an electrolyzer stack, and preferably theyare electrically connected in a vertical orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a typical electrolysis device.

FIG. 2 is a schematic representation of one embodiment of an improvedelectrolysis device in which first and second chambers are orientedperpendicular with respect to each other.

FIG. 3A is a cross-sectional schematic view of one embodiment of animproved electrolysis device showing first and second chamberspositioned concentrically in a vertical orientation.

FIG. 3B is an end schematic view of the embodiment of FIG. 3A.

FIG. 4 is an end schematic of one alternative embodiment of the deviceof FIG. 3A wherein there are multiple second chambers positioned withina large diameter first chamber.

FIG. 5 is a detailed view of metal particles in the upper chamber.

FIG. 6 plots the number of atoms on the surface of nanoparticlesrelative to particle diameter.

FIG. 7 is a chronovoltammetric plot showing the effect of metal particleaddition.

FIG. 8 is a bar graph describing the change in voltage with the additionof different sized metal particles.

FIG. 9 is a polarization curve illustrating system performance at highcurrent.

FIG. 10 is a bar graph illustrating comparing hydrogen generation on afluidized bed versus other electrodes.

FIG. 11 is a schematic end-on view of a fluidized bed reactor in spiralorientation.

FIG. 12 is a schematic end-on view of a fluidized bed wherein theelectrode is substantially horizontal and the separator is substantiallyvertical.

FIG. 13 is a schematic perspective view of a fluidized bed wherein theelectrodes and separators deviate from horizontal and the insulator issubstantially vertical.

FIG. 14 is a schematic end-on view of a fluidized bed wherein theelectrode and separator are conical.

FIG. 15 is a schematic end-on view of a fluidized bed wherein theelectrode and separator are substantially vertical.

The features mentioned above in the summary of the invention, along withother features of the inventions disclosed herein, are described belowwith reference to the drawings of some preferred embodiments. Theillustrated embodiments in the figures listed below are intended toillustrate, but not to limit the inventions.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS

FIG. 1 illustrates a traditional electrolysis system. The main featuresof this system are pumps circulating at the anode and cathode to removeresulting oxygen and hydrogen gasses, respectively. The electrodes aretypically oriented in a vertical fashion and are substantially solid.Oxygen and hydrogen gasses are scrubbed from the electrode beforeelectrolyte returns to the cell. Electrodes are typically solid metal orelectrodeposited metal with relatively low surface area.

Referring to FIG. 2, one embodiment of an inventive electrolyzerconfigured to generate hydrogen and oxygen from water can be described.Electrolyte 201, such as aqueous potassium hydroxide (KOH), sodiumhydroxide (NaOH), or a mixture of the two may be placed in a firstchamber 202 via inlet port 203. When electricity is applied to cathodeelectrode 204 through electrical contact 205, hydrogen gas is producedby 2H₂O+2e⁻→H₂+2OH⁻. Because hydrogen gas is less dense than theelectrolyte, it rises and leaves via port 206 to be collected orconsumed. Hydroxyl ions produced in the reaction permeate downwardthrough separator membrane 207. In a second chamber 208, electrolyte 201is circulated parallel to anode electrode 209 via inlet port 211 andoutlet port 210. In a preferred operative mode of at least one systemembodiment, the system is oriented such that the first chamber 202 ispositioned above the second chamber 208. Such an arrangement providessome advantages as discussed herein. It is contemplated, however, thatanother embodiment may comprise a system that is usefully oriented insuch a manner that the first chamber is horizontally displaced relativeto the second chamber, either in a side-by-side arrangement, or at someangle between vertical and horizontal.

When electricity is applied to electrode 209 via electrical contact 212,oxygen is produced pursuant to the following general reaction:2OH—→H₂O+½O₂+2e−. Oxygen is eliminated from the electrolyte streambefore the electrolyte is returned to the cell. To ensure that alloxygen is being eliminated from the upper surfaces of the lower chamber,angled deflector 213 is placed proximal to port 211 to ensure thatdeoxygenated electrolyte is washing the separator 207. For some systemmeasurements, a side chamber containing separator mat 214 is filled withelectrolyte 201, and reference electrode 215 is placed to measureelectrochemical potential versus the upper chamber. Additionally,working reference electrode 216 is placed in contact with electrode 204.

The system configuration illustrated in FIG. 2 has several distinctadvantages compared to the traditional electrolyzer shown in FIG. 1. Intraditional electrolyzers, the entire volume of electrolyte fed into thesystem requires pumping and removal of hydrogen and oxygen gasses fromthe cathode and anode streams, respectively, resulting in parasiticlosses. In the disclosed invention, the upper chamber acts on gravityand the electrolyte is stationary; hydrogen gas escapes from the topsurface and inherently travels to the upper outlet port because it isless dense than both the electrolyte and air. Only the lower chamberrequires electrolyte pumping to move oxygen out of the cell and flushnew electrolyte into the system, thus this system has only half theparasitic loss of a traditional system.

The cathode electrode in the upper chamber has increased efficiencyrelative to a conventional electrode, in that reacting hydroxyl ionsleave from the bottom of the electrode and resulting gas leaves from thetop of the electrode. This minimizes ionic resistance in the device, asgas bubbles do not block catalyst sites on the electrode to outgoinghydroxyl ions or incoming water molecules.

In the lower chamber of the device, an angled deflector is placedproximal to the electrolyte inlet port. Because the electrolyte flows ina parallel fashion to the electrode surface and product gas rises, it ispossible for gas bubbles to become lodged on the upper surface of thechamber proximal to the separator membrane, which can impede both waterand ionic transport. By deflecting electrolyte to the upper surface ofthe chamber, the increased flow force of the electrolyte on that surfaceprevents gas bubbles from lodging and results in improved systemefficiency.

In some of the preferred embodiments, the upper chamber features both aninlet and outlet port. One of the ports allows the removal of hydrogengas from the system, and the other allows for direct injection of newelectrolyte, compensatory water, or new catalyst. This feature allowsfor both simple cleaning and replenishment or replacement if catalystand reactants.

Some of the preferred embodiments detail an increased available reactionsurface through the use of porous electrodes. The electrodes can beprepared of networking metal particles, for example reticulate nickel ornickel foam. In other embodiments, the electrodes may be sintered metalplates, prepared such that the electrode is highly porous with arelatively large void volume. The electrodes are preferably preparedfrom metals, preferably selected from the group of metals from groups3-16, the lanthanide series and combinations thereof and alloys thereof.More preferably, the metals are transition metals, mixtures thereof, andalloys thereof and their respective oxides. Most preferably, the metalor metals are selected from the group consisting of nickel, iron,manganese, cobalt, tin, and silver, or combinations, alloys, and oxidesthereof.

An aspect of at least some of the embodiments in this invention includesthe realization that a reticulate or porous electrode's surface area canbe increased significantly through the use of free moving reactive metalparticles within the electrolyte. The electrolyte serves as both anionic conductor and medium for the particles. Because of the reticulateor porous nature of the electrode, reactive metal particles can infuseinto the electrode surface and become diffuse throughout the voidvolumes in the electrode. Preferably, the particles are less than onemicron in effective diameter, and more preferably less than 100nanometers in diameter. Most preferably, the reactive metal particlesare less than 50 nm in diameter such that substantial portion can infuseinto the electrode. Larger particles tend to agglomerate to the extentthat the void volume within the electrode can no longer accommodatetheir size. This results in a significant loss in efficiency.

Referring to FIGS. 3A and 3B, another embodiment that comprises, inoperation, a fluidized bed electrolysis reactor. The reactor comprises acorrosion resistant container 301 having one or several possiblegeometric configurations. The particular embodiment shown is generallycylindrical, with a generally cylindrical separator membrane 302aligned, if so desired, concentrically with the container 301. Themembrane 302 defines two chambers, an anode chamber and a cathodechamber. Porous or reticulate electrodes are disposed on each side ofthe membrane 302. Anode electrode 303 is disposed on the outer surfaceand cathode electrode 304 is disposed on the inner surface. Both theanode chamber 305 and cathode chamber 306 are filled with ionicallyconducting electrolyte 307, such as aqueous potassium hydroxide.Electrolyte 307 contains a plurality of reactive metal nanocatalystsparticles 308 that are fluidized by the rising gasses in each chamber.Catalytic nanoparticles suspended in both the inner and outer chambersmake contact with the electrodes through a percolation pathway. Thispercolation pathway is established when a plurality of the catalyticnanoparticles make contact with the porous or reticulate electrode aswell as indirect contact through a chain of nanoparticles thatultimately make contact with the electrode. Electricity is applied tothe electrodes via cathode electrical contact 311 and anode electricalcontact 312. Oxygen is generated in the anode chamber. Because thedensity of oxygen is less than that of the electrolyte, it travelsupward and leaves the system via port 309. Hydrogen is generated in thecathode chamber. Because hydrogen is less dense than the electrolyte, ittravels upward and leaves the system via port 310. The movement of theseresulting gas bubbles effectively fluidizes the reactive metalnanoparticles in the electrolyte such that the fluidized bed isself-propagating.

The system configuration illustrated in FIGS. 3A and 3B has severaldistinct advantages compared to the traditional electrolyzer shown inFIG. 1. In traditional electrolyzers, the entire volume of electrolytefed into the system requires pumping and removal of hydrogen and oxygengasses from the cathode and anode streams, respectively, resulting inparasitic losses. In the disclosed device, pumping is eliminated when afluidized bed is established. Once fluidization occurs, considerablylarger amounts of gas can be produced compared to a traditionalelectrolyzer. In addition, the device could be scaled to any conceivablesize.

Referring to FIG. 4, multiple cells described in FIG. 3 can be connectedfor increased surface area and therefore increased hydrogen and oxygenproduction. Ions travel only a short distance through the separator,thus fluidized bed convection in both inner chambers 401 and outsidechamber 402 the individual cells is not disturbed. Cathode electrodecontacts 403 (negative terminals) would preferably be connected inparallel to the negative terminal of a power supply, and anode electrodecontacts 404 (positive terminals) would be connected to the positiveterminal of the power supply. Both the inside and outside volume of eachcell contains a plurality of metal catalyst nanoparticles suspended in afluidized bed when the device is operating. An additional advantage tooperating multiple cells in this configuration is that because surfacearea is increased, internal resistance decreases and lowers parasiticlosses. In this configuration seven cells are shown, however theconfiguration can be scaled with many more cells.

FIG. 5 illustrates an electrode infused with nanoparticles and withnanoparticles suspended in electrolyte. Electrode 501 is preferably ahighly reticulate or porous, and can accommodate the infusion ofnanoparticles 502 (shown as dots) that can diffuse throughout the voidspaces within the interior of the electrode 503 and free moving in theelectrolyte 504. When electricity 508 is applied to the electrode 501,water in the electrolyte that comes through separator 510 is split,producing hydrogen gas 505. The hydrogen gas 505 may diffuse upwardlyand out of the top surface of the electrode 501, bubbling to the surfaceof the electrolyte to escape the apparatus 506. This bubbling maintainsfluidization within the chamber. Meanwhile, hydroxyl ions 507 may movedownwardly and permeate the separator membrane 510.

An electrode with infused nanoparticles has a larger reaction surfacethan the electrode alone. To illustrate the concept, a catalyticnanoparticle 502 touches the surface of electrode 501 and collectselectrons 508, splitting two surrounding water molecules within theinterior of the electrolyte 504 into an H₂ molecule 505 and two hydroxylions 507. The gas lifts the nanoparticle off the surface of theelectrode 501, while a sister particle 511 replaces it to repeat thereaction. When the system is running at it's optimum, a fluidized bed isdesirably established between the electrolyte, nano-catalysts and thetiny hydrogen gas bubbles. At least one aspect of the preferredembodiments includes the realization that gas or liquid does notnecessarily need to be flowed into the bottom of the chamber once afluidized bed has been established. In the described embodiments, gassesreleased from electrochemical reaction establish fluidization in-situ. Asignificant energy savings is inherent by eliminating the need forcontinuous pumping.

Unlike a traditional electrolyzer, whose efficiency decreases as currentincreases, a fluidized bed electrolyzer described in the preferredembodiments will increase in efficiency as current is increased, until alimiting current is reached in which further gas generation disruptsfluidization and the percolation pathway, ultimately loweringefficiency. Nevertheless, this limiting current at maximum efficiency issignificantly higher in the devices described in the preferredembodiments compared to a traditional electrolysis system.

Additionally, reactive surface area is increased by order of magnitudeby operation with catalytic nanoparticles in the fluidized bed. Inaddition to the surface area of the porous or reticulate electrode, andnanoparticles infused into the electrode, the system capitalizes on theadditional surface area of the fluidized catalytic nanoparticles. Theincreased catalytic behavior of the reactive metal nanoparticles,compared to the surface of the metal substrate alone, is high due to thevery large number of atoms on the surface of the nanoparticles, as shownin FIG. 6. By way of demonstration, consider a 3 nanometer nickelparticle as a tiny sphere. Such a sphere would have 384 atoms on itssurface and 530 within its interior, of the 914 atoms in total. Thismeans that 58% of the nanoparticles would have the energy of the bulkmaterial and 42% would have higher energy due to the absence ofneighboring atoms. Nickel atoms in the bulk material have about 12nearest neighbors while those on the surface have nine or fewer. A 3micron sphere of nickel would have 455 million atoms on the surface ofthe sphere, 913 billion in the low energy and isolated interior of thesphere for a total of nearly one trillion atoms. That means that only0.05% of the atoms are on the surface of the 3 micron-sized materialcompared to the 42% of the atoms at the surface of the 3-nanometernickel particles.

The reactive metal particles can be formed through any knownmanufacturing technique, including, for example, but without limitation,ball milling, precipitation, plasma torch synthesis, combustion flame,exploding wires, spark erosion, ion collision, laser ablation, electronbeam evaporation, and vaporization-quenching techniques such as jouleheating.

Another possible technique includes feeding a material onto a heaterelement so as to vaporize the material in a well-controlled dynamicenvironment. Such technique desirably includes allowing the materialvapor to flow upwardly from the heater element in a substantiallylaminar manner under free convection, injecting a flow of cooling gasupwardly from a position below the heater element, preferably parallelto and into contact with the upward flow of the vaporized material andat the same velocity as the vaporized material, allowing the cooling gasand vaporized material to rise and mix sufficiently long enough to allownano-scale particles of the material to condense out of the vapor, anddrawing the mixed flow of cooling gas and nano-scale particles with avacuum into a storage chamber. Such a process is described more fully inU.S. patent Ser. No. 10/840,109, filed May 6, 2004, the entire contentsof which is hereby expressly incorporated by reference.

The chemical kinetics of catalysts generally depend on the reaction ofsurface atoms. Having more surface atoms available will increase therate of many chemical reactions such as combustion, electrochemicaloxidation and reduction reactions, and adsorption. Extremely shortelectron diffusion paths, (for example, 6 atoms from the particle centerto the edge in 3 nanometer particles) allow for fast transport ofelectrons through and into the particles for other processes. Theseproperties give nanoparticles unique characteristics that are unlikethose of corresponding conventional (micron and larger) materials. Thehigh percentage of surface atoms enhances galvanic events such as thesplitting of water molecules into its composite gasses of hydrogen andoxygen. FIG. 3 shows this relationship well.

The reactive metal particles referenced herein are preferably selectedfrom the group of metals from groups 3-16, and the lanthanide series.More preferably, the metals are transition metals, mixtures thereof, andalloys thereof and their respective oxides. Most preferably, the metalor metals are selected from the group consisting of nickel, iron,manganese, cobalt, tin, and silver, or combinations, alloys, and oxidesthereof. The nanoparticles may be the same as, substantially the same,or entirely different materials from those chosen for the electrode.Additionally, the nanoparticles may comprise a metal core and an oxideshell having a thickness in the range from 5 to 100% of the totalparticle composition, wherein the metal core may be an alloy.

In other preferred embodiments, new fluidized bed electrolyzer designsare shown. These designs improve performance by enhancing reactionefficiency and reducing size. In some designs, reaction efficiency maybe maximized when ionic resistance losses are reduced by minimizing thedistance between the separator membrane and electrode. In other designs,the electrodes may be formed into a smaller area allowing for a smallerfootprint.

Irrespective of design, a significant aspect of the preferredembodiments is adequate composition of the membrane separator. Theseparator should be able to operate at temperatures up to 130° C.,permit an ion flux exceeding 5 A/cm², maintain stability in stronglyalkaline solutions such as high concentration potassium or sodiumhydroxide, and prevent product gas bubbles from permeating between cellchambers. The membrane may be micro porous, such that electrolyte ispermitted to move between reaction chambers, or may be nonporous butionically conductive.

A spiral orientation of the fluidized bed reactor is illustrated in FIG.11, wherein porous negative and positive electrodes 1101 and 1102,respectively are rolled between separator 1103. Catalytic particles arethen injected into electrolyte 1104. Electrically insulating material1105 is employed at the center of the spiral as well as at the electrodeand separator outer termination points. The advantage to thisconfiguration is that high surface area current collector electrodes canoccupy less volume and therefore a smaller device can be employed toproduce the amount of reaction products only achieved in a largersystem. To encapsulate the reactor, solid negative and positiveelectrodes 1106 and 1107, respectively, are used as the outer walls.

In another aspect of the preferred embodiments, a fluidized bed reactormay be established wherein the current collector is in a horizontalconfiguration and the separator membrane is in a vertical orientation.Referring to FIG. 12, separator membrane 1201 serves as a partitionbetween the anode and cathode sides of the cell. Cathode and anodeporous electrodes 1202 and 1203 are placed at the bottom of the reactionvessel, and catalytic particles are injected into electrolyte 1204 inboth the anodic and cathodic chambers. The catalytic particles aresuspended by the gasses they produce and form an electrically conductivemass in each chamber. The resulting ions have only a short distance totravel to the opposing chamber to complete the circuit.

Referring to FIG. 13, porous electrodes 1301 and 1302 may be orientedaway from horizontal position such that a space is provided under theelectrode. Separator 1303 is disposed on the bottom face of theelectrodes. This space may be filled with an electrolyte 1304 such asKOH in gel form to serve as an ion bridge between the two electrodes.Insulator 1305 serves to keep catalytic particles and product gassessegregated. This configuration may be advantageous in improving theestablishment of a fluidized bed since both current collectors are onlydegrees from horizontal. Referring to FIGS. 14A and 14B, electrodes 1401and 1402 with separator 1403 disposed on the lower surface may be formedinto a cone configuration. Insulator 1405 bisects the cone through theporous electrode and separator to maintain polarized reaction zones, andliquid electrolyte 1406 serves as an ion conduction medium for theaddition of reactive catalytic particles. Electrical contact leads maybe connected to 1401 and 1402 to permit the flow of electricity.

Additionally, the electrodes and separator may be oriented vertically.Referring to FIG. 15, porous anode and cathode electrodes 1501 an 1502are proximally disposed on either face of separator 1503. Catalyticparticles are injected into electrolyte 1304. In this configuration,multiple cells may be connected in series through repeating units or inseries. Negative and positive leads 1505 and 1506 are connected toelectrodes 1501 and 1502 to permit the flow of electricity.

The foregoing description is that of preferred embodiments havingcertain features, aspects, and advantages in accordance with the presentinventions. Various changes and modifications also may be made to theabove-described embodiments without departing from the spirit and scopeof the inventions.

Example 1 Effect of Nanoparticle Addition to Upper (Cathode) Chamber

The water electrolysis device shown in FIG. 2 was used to perform theexperiment. FIG. 7 illustrates the effect of injecting nano-catalystinto the upper chamber of the water electrolysis device. Theelectrolyzer is allowed to reach a steady-state voltage under 1 A/cm²,which is evident after about 60 seconds. At time 701, nickelnanoparticles (QSI-Nano® Nickel, 5-30 nm, from QuantumSphere Inc.) wereadded to the upper chamber of the electrolyzer. An efficiency increaseof 10% was observed after addition of nickel nanoparticles 502. Afterabout 15 minutes, steady state efficiency improvement was about 20%.

Example 2 Comparison of Five Different Cathode Electrodes

FIG. 8 compares the performance of several different cathode electrodesfor a water electrolysis device. Electrodes compared are Incofoam nickelmetal foam (purchased from Inco), a sintered micron nickel plate (asintered, compressed electrode of 1-5 micron Ni particles, purchasedfrom Alfa Aesar), a sintered nickel plate of nickel particles (Inco 123,purchased from Inco), a sintered electrode of 5-30 nm nano-nickel fromQuantumSphere Inc, and a sintered plate prepared from 1-5 micron nickelparticles, as above, with 10 wt % 5-30 nm nickel from QuantumSphere Inc.injected into the electrolyte. An improvement over the base electrode801 with no catalytic powders added was observed when micron particleswere added 802 on a 1 Amp/cm² load. This combination, however,agglomerated after less than an hour of running with significantdegradation. The addition of nano-catalyst 803 increased the performanceby nearly 4 times compared to the unanalyzed electrode 801. Forreference, a 10% improvement line 804 is included in the FIG. 5.

Example 3 High Rate Capability of Electrolysis Device

FIG. 9 illustrates the improved rate capability of the electrolysisdevice described in the preferred embodiments relative to a moretraditional system. This figure shows the voltage and currentrelationship of several electrode designs. Sets 901-904 are of a designcompressed powders, as shown in Example 2. Sets 905-906 show thepreferred embodiment. Specifically, data sets 901/901′ show a carbonelectrode, 902/902′ show a smooth nickel electrode, 903/903′ show acompressed micron sized nickel electrode, 904/904′ show a micron nickelwith nano sized powders added then compressed, 905/905′ show thepreferred embodiment with no added catalyst, and 906/906′ show the mostpreferred embodiment (a foam nickel electrode with nano-nickel particlesinjected.) with nano-catalyst added. A voltage difference of 2 volts isabout 75% efficiency. The last set of dots, 907, is a cell potential of1,584 volts and represents over 90% efficiency when calculating theenergy in the hydrogen divided by the energy it takes to electrolyze thewater to make that hydrogen. The best traditional electrolysis systemsoperate at less than 75% efficiency when run higher than 0.5 A/cm².

Example 4 Effect of Fluidized Bed

FIG. 10 shows the performance of five experiments with the mostpreferred embodiment to the right. Performance is expressed as theamount of hydrogen (as gge or gallon of gas equivalents) per hour persquare meter of electrode surface. The set of comparisons is a graphiteelectrode 1001, a micron nickel catalyzed electrode 1002, a nano nickelcatalyzed electrode 1003, an electrode catalyzed using three differentnano sized catalysts 1004 and the fluidized bed electrolyzer 1005.Another way to compare these would be the amount of time it would takefor a one square meter electrode to produce one gge. Table 1 belowsummarizes that data. The graphite produces hydrogen at 85% efficiencyvery slowly, requiring 32 days to make one gge while the fluidized bedtakes just 25 minutes.

TABLE 1 Comparison of electrode rates from several different electrodedesigns. Design Hr/gge/m{circumflex over ( )}2 Graphite (1001) 769 uNickel (1002) 125 QSI nNi (1003) 25.0 3 QSI nCatalysts (1004) 3.85 Newwith QSI Catalysts (1005) 0.412

1. A device suitable for use in an electrochemical and/or catalyticapplication, the device comprising a first component and a secondcomponent, said first component being at least partially exposed to areaction medium during use, the second component comprising a pluralityof reactive metal nanoparticles suspended in the reaction medium anddiffused into the first component when the device is in use.
 2. Thedevice of claim 1, wherein the first component comprising a metal havinga substantial void volume.
 3. The device of claim 1, wherein at least asubstantial portion of the plurality of reactive metal particlescomprises particles have an average diameter of less than about 100 nm.4. The device of claim 1, wherein at least a portion of the reactivemetal particles comprise nanoparticles having an oxide shell.
 5. Thedevice of claim 1, wherein the plurality of reactive metal particlescomprise one or more of the metals from groups 3-16, lanthanides,combinations thereof, and alloys thereof.
 6. The device of claim 2,wherein the first component is a sintered porous metal plate.
 7. Thedevice of claim 2, wherein the first component is a reticulate metalplate.
 8. The device of claim 1, wherein the first component comprisesone or more of the metals from groups 3-16, lanthanides, combinationsthereof, and alloys thereof.
 9. The device of claim 1, wherein thedevice comprises an electrolysis cell whereby reaction products areproduced when energy is applied.
 10. The device of claim 9, wherein thedevice is configured to generate hydrogen from water.
 11. Anelectrochemical system, comprising: a first chamber comprising anelectrode, electrolyte, and metal catalyst particles arranged such that,when in operation, a zone in the nature of a fluidized bed may beestablished in the electrolyte and gaseous products produced by thesupply of electricity to the system may be removed from the firstchamber;
 12. The electrochemical system of claim 11, further comprising:a second chamber, the first chamber being partitioned from the secondchamber by a separator, the second chamber comprising an electrode,electrolyte, and metal catalyst particles arranged such that, when inoperation, a fluidized bed may be established, and gaseous products areremoved from the second chamber.
 13. The electrochemical system of claim12, wherein the first and second chambers are arranged with the firstchamber at least partially above the second chamber, at least partiallyaround the second chamber, at least partially displaced laterally withrespect to the second chamber, or at least partially coiled around thesecond chamber.
 14. The electrochemical system of claim 13, wherein thefirst chamber is positioned at least partially above the second chamber,the second chamber having an inlet and an outlet and being configuredsuch that electrolyte circulated through the second chamber when in usemay flow from the inlet past the second chamber electrode to the outletin a generally transverse direction and, when in use, reactants may fluxin the first chamber and gases generated in the first chamber may moveupwardly for collection.
 15. The electrochemical system of claim 14,further comprising a pump to circulate at least a portion of theelectrolyte in the second chamber.
 16. The electrochemical system ofclaim 13, wherein the system is configured and adapted to permit usefuloperation while being oriented such that the first chamber is positionedat least partially horizontally displaced from the second chamber. 17.The electrochemical system of claim 11, wherein the electrolyte in thefirst chamber is generally confined to that space.
 18. Theelectrochemical system of claim 14, further comprising a plurality ofreactive metal particles in the upper chamber suitably sized to permitparticle diffusion into voids within one or both of the electrodes. 19.The system of claim 11, wherein at least a substantial portion of thereactive metal particles have an average diameter of less than onemicrometer.
 20. The system of claim 19, wherein the nanoparticles havean average diameter of less than about 100 nm.
 21. The system of claim11, wherein the plurality of reactive metal particles comprises a metalselected from the group consisting of metals from groups 3-16,lanthanides, combinations thereof, and alloys thereof.
 22. The system ofclaim 3, wherein the separator comprises a membrane formed from anionically conductive material.
 23. The system of claim 22, wherein theseparator membrane comprises multiple layers of ionically conductivematerial to increase mechanical, chemical, and electrochemicaldurability.
 24. The system of claim 22, wherein the separator membraneis capable of at least 5 A/cm² flux.
 25. The system of claim 14, whereinthe electrolyte flow channel of the second chamber contains a deflectorto aid in transport to the separator surface.
 26. The system of claim 3,wherein the first chamber electrode is configured to generate hydrogenfrom water and the second chamber electrode is configured to generateoxygen from water.
 27. An electrochemical system, comprising: a firstchamber and a second chamber, the first chamber being disposed withinthe second chamber when the system is oriented such that it can be usedin at least one useful purpose, the first chamber comprising anelectrode, electrolyte, and metal catalyst particles arranged such that,when in operation, a fluidized bed may be established, and gaseousproducts may be removed from the upper portion of the first chamber; thesecond outer chamber comprising an electrode, electrolyte, and metalcatalyst particles arranged such that, when in operation, a fluidizedbed may be established, and gaseous products are removed from the upperportion of the second chamber.
 28. The system of claim 27, furthercomprising a separator membrane disposed between the first and secondchambers.
 29. The system of claim 27, further comprising electricalcontacts on the first and second electrodes to permit the flow ofelectricity therebetween.
 30. The system of claim 27, wherein theelectrolyte in the first chamber is generally confined to that space.31. The system of claim 27, wherein the electrolyte in the secondchamber is generally confined to that space.
 32. The system of claim 27,wherein at least a substantial portion of the reactive metal particleshave an effective diameter of less than one micrometer.
 33. The systemof claim 27, wherein the particles have a diameter of less than about100 nm.
 34. The system of claim 27, wherein the plurality of reactivemetal particles comprises a metal selected from the group consisting ofmetals from groups 3-16, lanthanides, combinations thereof, and alloysthereof.
 35. The system of claim 28, wherein the separator membranecomprises an ionically conductive material.
 36. The system of claim 35,wherein the separator membrane comprises multiple layers of ionicallyconductive material to increase mechanical, chemical, andelectrochemical durability.
 37. The system of claim 27, wherein thefirst chamber electrode is configured to generate hydrogen from waterand the second chamber electrode is configured to generate oxygen fromwater.
 38. The system of claim 27, wherein a multiple of first innerchambers are placed within a single outer chamber, and where each innerchamber is electrically connected in a circuit with the outer chamber.39. The system of claim 38, wherein the first chamber electrode isconfigured to generate hydrogen from water and the second chamberelectrode is configured to generate oxygen from water.
 40. Anelectrochemical system, comprising: a first chamber and a secondchamber, the first chamber being separated from the second chamber by aseparator membrane when the system is oriented such that it can be usedin at least one useful purpose, the first chamber comprising a currentcollector, electrolyte, and metal catalyst particles arranged such that,when in operation, a fluidized bed may be established, and gaseousproducts may be removed from the upper portion of the first chamber; thesecond outer chamber comprising an electrode, electrolyte, and metalcatalyst particles arranged such that, when in operation, a fluidizedbed may be established, and gaseous products are removed from the upperportion of the second chamber.
 41. The system of claim 40, furthercomprising electrical contacts on the first and second electrodes topermit the flow of electricity therebetween.
 42. The system of claim 40,wherein the current collector and separator is wound into a spiral. 43.The system of claim 40, wherein the electrolyte in the first chamber isgenerally confined to that space.
 44. The system of claim 40, whereinthe electrolyte in the second chamber is generally confined to thatspace.
 45. The system of claim 40, wherein the separator is microporous.46. The system of claim 40, wherein the separator is nonporous andion-conducting.
 47. The system of claim 40, wherein the separatormembrane comprises multiple layers of ionically conductive material toincrease mechanical, chemical, and electrochemical durability.
 48. Thesystem of claim 40, wherein the separator is capable of permitting thetransport of at least 5 A/cm² current flux.
 49. The system of claim 40,wherein the current collector is generally horizontal and the separatoris generally vertical.
 50. The system of claim 40, wherein the currentcollector and separator are generally vertical.
 51. The system of claim40, wherein the current collector and separator are conical.
 52. Thesystem of claim 40, further comprising an insulating sheet.
 53. Thesystem of claim 40, wherein the current collector is porous orreticulate.
 54. The system of claim 40, wherein the current collectorprotrudes into the fluidized bed.
 55. The system of claim 40, wherein atleast a substantial portion of the reactive metal particles have anaverage diameter of less than one micrometer.
 56. The system of claim40, wherein the particles have an average diameter of less than about100 nm.
 57. The system of claim 40, wherein the plurality of reactivemetal particles comprises a metal selected from the group consisting ofmetals from groups 3-16, lanthanides, combinations thereof, and alloysthereof.
 58. The system of claim 40, wherein the first chamber electrodeis configured to generate hydrogen from water and the second chamberelectrode is configured to generate oxygen from water.
 59. A method ofoperating an electrochemical cell, which cell comprises an anode chambercontaining electrolyte and an anode, a cathode chamber containingelectrolyte and a cathode, which method comprises suspending reactivemetal particles in the anode chamber and/or the cathode chamberelectrolyte, and applying electricity such that a circuit is formed. 60.A method of claim 59, comprising suspending reactive nanoparticles in atleast the cathode chamber and forming in the electrolyte in the cathodechamber a reaction zone in the nature of a fluidized bed to increase theeffective area of the cathode and transport gas produced by the reactionfrom the chamber.
 61. A method of claim 59, comprising also suspendingreactive nanoparticles in the anode chamber and forming therein areaction zone in the nature of a fluidized bed to transport gas formedin the anode chamber from the chamber.
 62. A method of claim 60, whereinthe electrolyte comprises an aqueous salt solution and the methodcomprises producing hydrogen in the cathode chamber and forming in thatchamber from the hydrogen, electrolyte and particles a system akin to afluidized bed whereby the hydrogen bubbles upwardly through theelectrolyte, the method further comprising collecting the hydrogen soproduced.
 63. A method of claim 59, wherein the particles have anaverage diameter of less than about 100 nm.
 64. A method of claim 59,wherein the particles have an average diameter of less than about 50 nm.